Modulation and TB size modulation two-layer spatial multiplex additionally a translation table has to be applied.
In case of DCI format 1C a separate table is used.

Modulation and TB size

A 5-bit “modulation and coding scheme” yields the modulation order, i.e. QPSK,
16QAM or 64QAM. Implicitly the coding rate is given by a combination of the number of scheduled RBs and the signaled TB size.

The determination is based on the signaled MCS Index IMCS.

By means of a 27×110 table the resulting TB size can be determined. Part of the
table (for non two-layer spatial multiplex) is shown in the figure. A graphical display is shown below.
Note, for two-layer spatial multiplex additionally a translation table has to be applied.
In case of DCI format 1C a separate table is used.